1. Field of the Invention
The invention relates to a plasma producing method and apparatus for producing gas plasma as well as a plasma processing apparatus using the plasma producing apparatus, i.e., a plasma processing apparatus effecting intended processing on a work or target in plasma.
2. Description of the Related Art
Plasma is used, e.g., in plasma CVD method and apparatus forming a film in plasma, method and apparatus forming a film by effecting sputtering on a sputter target in plasma, method and apparatus performing etching in plasma, and method, apparatus and the like used for performing ion implantation or ion doping by extracting ions from plasma. Further, the plasma is used in various apparatuses utilizing the plasma such as apparatuses producing various semiconductor devices (e.g., thin-film transistors used in liquid crystal displays or the like), material substrates thereof or the like by using the foregoing methods and/or apparatuses.
Various types of plasma producing methods and apparatuses have been known and, for example, such types have been known that produces capacitively coupled plasma, produces inductively coupled plasma or ECR (Electron Cyclotron Resonance) plasma or produces microwave plasma.
Among them, the plasma producing method and apparatus producing the inductively coupled plasma are configured to obtain plasma of extremely high density and uniformity in a plasma producing chamber and, for this purpose, has a high-frequency antenna for the plasma producing chamber for producing the inductively coupled plasma by applying a high-frequency power from the high-frequency antenna to a gas in the chamber. More specifically, the high-frequency power is supplied to the high-frequency antenna to generate an induction electromagnetic field in the plasma producing chamber, and the induction electromagnetic field produces the inductively coupled plasma.
The high-frequency antenna may be arranged outside the plasma producing chamber, but it is also proposed to arrange it inside the plasma producing chamber for improving use efficiency of the supplied high-frequency power and other purposes.
For example, it is described in Japanese Laid-Open Patent Publication No. 2004-200233 (JP2004-200233A) that high-frequency antennas are arranged inside a plasma producing chamber, and the plurality of high-frequency antennas arranged in the plasma producing chamber are successively and linearly arranged on the same plane, and the neighboring electrodes of the neighboring antennas have the same polarity to uniformize the plasma density distribution and improve the plasma density,.
An electron temperature (in other words, energy of electrons) in the plasma affects cutting of interatomic coupling of a substance exposed to the plasma, and the higher electron temperature causes cutting of the interatomic coupling to a higher extent. In the plasma processing, therefore, it is desired to control the electron temperature of the plasma and particularly to lower the electron temperature, e.g.,for the purpose of suppressing damages to a work and the like due to plasma, or performing desired etching processing. For example, in the case where a silicon thin film for a bottom-gate-type TFT is formed by a plasma CVD method, such a method is generally employed that the silicon thin film is formed on a substrate on which a gate insulating film (e.g., made of silicon nitride, silicon oxide or a mixture thereof) was deposited. When the electron temperature of the plasma is high when forming the silicon thin film, defects may occur, e.g., at the gate insulating film or the silicon thin film.
In connection with this, Japanese Laid-Open Patent Publication No. H11-74251 (JP11-74251A) has disclosed that an ion temperature lowers when an electron temperature in plasma becomes equal to 3 eV or lower in the plasma CVD method, and therefore, ion damages to a target substrate can be lowered in the plasma CVD.
As a manner of setting the electron temperature of 3 eV or lower, it is disclosed to generate higher-density plasma in a projection portion of the plasma producing chamber (vacuum container), in which a static magnetic field for controlling the plasma state is not present, than in the vicinity of the work substrate.
Japanese Laid-Open Patent Publication No. 2004-311975 (JP2004-311975A) has disclosed that excessive decomposition of a material gas is prevented to form a good insulating film in the plasma CVD method by keeping the electron temperature at 3 eV or lower in a plasma generating space.
As a manner of setting the electron temperature at 3 eV or lower, it is disclosed to produce microwave plasma, and to employ a plane antenna member that is connected to a waveguide of the microwave and is provided with a large number of slits in a peripheral direction of the antenna member.
According to JP2004-200233A, the uniformity of the plasma density distribution and the plasma density can be improved by arranging the plurality of high-frequency antennas in the plasma producing chamber and employing the neighboring electrodes of the same polarity in the neighboring antennas. However, this reference has not referred to suppression of the electron temperature of the plasma.
JP11-74251A and JP2004-311975A have referred to suppression of the electron temperature. For such suppression, the former has disclosed that the higher-density plasma is generated in the projection portion of the plasma producing chamber (vacuum chamber), in which a static magnetic field for controlling the plasma state is not present, than in the vicinity of the work substrate. According to this structure, the plasma producing chamber (vacuum container) must have the projection portion in which a static magnetic field for controlling the plasma state is not present.
The latter has disclosed the structure producing the microwave plasma, and employing the plane antenna member that is connected to the waveguide of the microwave and is provided with the large number of slits in a peripheral direction of the antenna member. It is necessary to prepare the antenna member having such a structure.